Transesterification Reaction of Cellulose with Inactive Esters in Ionic Liquids Acting as Both Catalysts and Solvents

Aryloxy Ionic Liquid-Catalyzed Homogenous Esterification of Cellulose with Low-Reactive Acyl Donors

“…Then, the hydroxy groups of cellulose nucleophilically attack the carbonyl carbon of the mixed acid anhydride, leading to side reactions [ 22 , 23 ]. Based on this finding, the design of ILs with different carboxylate anions was investigated in our previous reports to prevent the generation of mixed acid anhydrides and proceed with the desired acylation with high selectivity [ 24 , 25 ]. ILs with optimized anion substituents and bulkiness, for example, 1-ethyl-3-methylimidazolium p -anisate (EmimOAn 2 ), were able to suppress the formation of mixed acid anhydrides while maintaining high cellulose solvation and transesterification reactivity [ 24 ].…”

Transesterification of cellulose with unactivated esters in superbase–acid conjugate ionic liquids

“…22 Recently, ILs composed from the 1-ethyl-3-methylimidazolium cation and different carboxylate anions e.g., acetate, benzoate, pivalate, etc., have shown promising potential as they have not only served as solvents, but also as catalysts in the synthesis of cellulose esters. [23][24][25] However, the catalytical activity of the imidazoliumbased ILs could originate from carbene formation during the reaction and/or from the mixed anhydride formation between the anions and the acyl donors. [26][27][28][29] Even though these ILs can produce cellulose esters with high DS, the mixed anhydride formation (with the carboxylate anion of the IL) oen leads to mixed esterswhich can complicate recycling of the IL.…”

Direct Synthesis of Full-Biobased Cellulose Esters from Essential Oil Component α,β-Unsaturated Aldehydes

“…Especially, there is growing interest in using ILs in cellulose modification and developing new cellulose derivatives as plastics . This modification for cellulose-derived polymers is useful in various applications, such as controlling the interfacial interactions when forming composite materials. , Nevertheless, all reported syntheses of cellulose esters still employ the classical esterification process that uses synthetic reagents (acid chlorides, acid anhydrides, or active esters) and generates corresponding wastes. ,,,− Recently, environmentally friendly cellulose esterification through transesterification between cellulose and inactive alkyl esters, which are also abundant in nature, has been reported, although it has some points to be improved, such as the need for a high reaction temperature (∼100 °C) or a superbase for the reaction to proceed efficiently. − Thus, it is necessary to develop new green esterification processes with better atom economy. , …”

“…Besides cinnamaldehyde, other α,β-unsaturated aldehydes are also abundant in the essential oils of plants, such as citral, 2-hexenal, and perillaldehyde. − However, when using carboxylate-type ILs presented by commercially available 1-ethyl-3-methylimidazolium (Emim) acetate (OAc) for the esterification reaction, the anion in the IL is inevitably mixed into the polymer as an ester group due to the generation of mixed acid anhydride, ,,,, and it is difficult to completely suppress the problem of anion introduction as an ester group on the product and obtain the product polymer consisting of the full-biobased single-ester group in the strict sense. We previously developed Emim phenylpropionate (EmimPPA) as an appropriate IL for use with cinnamaldehyde to improve the appearance for the synthesis of the formally full-biobased polymer.…”